Proceedings - C-SRNWP Project

Aladin consortium activities in data assimilation
Claude Fischer & Andras Horanyi
Météo-France/CNRM ; Hungarian Meteorological Service
contributors: Fatima Karbou, Pierre Brousseau, Loïk Berre, Olivier Caumont, Zahra
Sahlaoui, Simona Stefanescu, Alex Deckmyn
The Aladin consortium pursues the development of its variational assimilation facility, in
close software interaction with the IFS/Arpège global system, and some first applications at
the convective scale in the frame of the Arome project. In the two previous years, significant
efforts have been spent for preparing the progressive convergence of this tool with the Hirlam
system and plans for mesoscale data assimilation. We show in our note some prominent
activities of the last year and draw perspectives in terms of development and collaborations.
1. Mainframe 3D-VAR: example of Aladin-France
Below are listed the most important technical features of the Aladin assimilation system, as
far as its variational component for upper air fields is concerned, based on the example of the
French application (Fischer etal., 2005):
►Incremental 3D-VAR
►Continuous assimilation cycle, 6 hour frequency, long cut-off assimilation cycle and short
cut-off production, coupled with Arpège, Analysis=Model gridmesh=9.5km
►Observations:
• Surface pressure, SHIP winds, synop T2m and RH2m
• Aircraft data
• SATOB motion winds
• Drifting buoys
• Soundings (TEMP, PILOT)
• Satellite radiances: AMSU-A, AMSU-B, HIRS, Meteosat-8 SEVIRI
• QuikSCAT winds
• Ground-based GPS zenital delays
►Digital filter initialisation (non incremental)
2. Background error covariance modelization
2.1. Non-linear and omega balances
Based on the work by Mike Fisher for the IFS, we have adapted the Aladin balance
formulations in order to apply a quasi-geostrophic omega equation and a non-linear balance
constraint. Figure 1 shows the effect on the analysis increment for a single observation of
temperature.
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